Well tools



Feb. 14, 1961 MARSH 2 971582 WELL TOOLS 2 Sheets-Sheet 1 Filed Aug. 29, 1958 Gare/d f. MdrJ/V INVENTOR.

A TrdRA/EV G. E. MARSH Feb. 14, 1961 WELL TOOLS 2 Sheets-Sheet 2 Filed Aug. 29, 1958 Gar 6/0 15 Marv/2 INVENTOR.

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United St tes Pflt o F WELL TOOLS Gareld E. Marsh, Houston, Tex., assignor to Schlumberger Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed Aug. 29, 1958, Ser. No. 757,954

7 Claims. (Cl. 166-241) The present invention relates to well tools and, more particularly, to new and improved means for centering a well tool in a well bore and for maintaining thebody of the well tool a spaced distance from the wall of the well bore. i

In certain well surveying operations, a well tool may include a plurality of circumferentially spaced wall-engaging members interlinked with respect to one another and arranged to contact the sidewall while being passed through a well bore. Obviously, a well tool has a weight component in a radial direction relative to the tool body which increases with increasing inclination of the borehole and thus wall contact or centering action, as the case may be, of the wall-engaging members may be undesirably impaired whenever the radial weight component exceeds the force with which the wall-engaging members are extended. The centering action or force of the wall-engaging member is independent of the angle.

of inclination. Thus increasing the centering force .of the wall-engaging members in an attempt to overcome the radial weight component for extreme inclinations would increase the friction between the wall-engaging members and sidewall to a degree which impede, if not completely retard, passage of the tool through the borehole. Furthermore, if the friction forces-are increased, then a greater pulling force on the cable is required to pull the tool upwardly through the bore which increases the cable tension. Hence, when irregularities in the bore are encountered by the wall-engaging members, a rocking and erratic movement of the tool will result. At the same time, undesirable wall damage may occur by virtue of the erratic movement of thetool.

Obviously, with the above-described tool, acentering device can be additionally employed to asume the radial weight component of the tool thereby reducing the centering force for the wall-engaging members. However, conventional spring-type and other known devices also have a centering force independent of the anglc of inclination so that if the centering force is suificient to balance the radial Weightcomponent for the largest inclination to be encountered, the movement of the well tool is again impeded-and damage to the sidewalls may also be incurred. Of course, if the radial weight component exceeds the centering force on the wall-engaging members the centering device collapses, and the wall contact of the wall-engaging members is impaired.

It is therefore desirable to provide centralizing means for a well tool which does not require excessive center:

ing strength while at the same time will support the radial weight, component of the tool in moderate to highly inclined boreholes so that the tool body does not come into contact with the sidewalls.

Accordingly, an object of the present invention is to provide new and improved arm construction for central.- izing means for a well tool.

Another object of the present invention is to provide a new and improved arm construction for centralizing means having a relatively small arm length.

Patented Feb. 14, 1961 ice It is a further object of this invention to provide new and improved means of supporting the radial weight component of a well tool having wall-engaging members in an inclined well bore so that the centering strength necessary for the supporting means to maintain the wall-engaging members in contact with the sidewalls of a well bore may be minimized.

Yet another object of the present invention is to provide new and improved means of supporting the radial weight component of a well tool having wall-engaging members in a highly inclined well bore while minimizing the frictional forces of the wall-engaging members on the walls oftthe well bore. 7

A still further object of the present invention is to prm vide new and improved means of supporting the radial weight component of an elongated tool in an inclined well bore wherein the means provides a fulcrum to balance and space the body of the tool away from the sidewall of the well bore to facilitate balancing of other forces. acting on the tool.

These and other objects are attained by centralizing means comprised of a plurality of circumferentially spaced arm members disposed at the center of balance of an elongated tool. The arms are constructed of an elastic material having supporting members embedded therein to prevent lateral bending yet permitting limited longitudinal flexing of the arms in highly deviated Well bores to a minimum radial dimension relative to the tool body thereby to support the tool body at a spaced distance from the sidewalls of the well bore.

The novel features of the present'invention are set forth with particularity in the appended claims. The present invention both as toits organization and manner of operation together with further objects and advantages thereof may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

Fig. 1 is an elevational view of a centralizing means embodying the present invention shown on a well tool disposed in a portion of a well bore which is inclined atan angle of approximately 15 from the vertical;

Fig. 2 is a view similar to Fig.1 showing a well bore at an inclination angle of about 45 from the vertical; Fig. 3 is a view looking down on a tool similar to the one shown in Fig. 1, but drawn to an enlarged scale and illustrating a preferred angular relationship of the cen-' tralizing means relative to the wall-engaging means of the tool;

Fig. 4 is a view in cross section taken along lines 44 of Fig. 3 and illustrating the details ofone of the tralizing armsjand.

Fig. 5 is a plan. view of the centralizing arm shown in:

by means of a cable 12 securedto its'upper end. Cable I 12 extends upwardly to the surface and suitable means (not shown) are provided to lower and raise the cable in the well bore in a well-known manner. The cablefunctions not only to support the tool but also to provide electrical conductors (not shown.) for electrical connec- "2,971,582 V v V g and spaced circumferentially about the tool body are a plurality of centralizing arms 19. While only three arms are shown (Fig. 3), it will be readily apparent that this number may be varied ,as desired. 7 At thelower end of toolll are a plurality of wall-engagingpads spaced circumferentially about the tool body. .Pads 20 may be varied in number and location as desired, For convenience of illustration, the arms 19 and pads 20 in Figs. 1 and 2 are illustrated in longitudinally aligned planes, however, as will be apparent from a discussion hereinafter of Fig. 3, in a preferred alignment the supporting arms 19 are angularly displaced '60 with respect to the wall-engaging pads 20 so that the portion of the well bore traversed by the pads 20 is undisturbed bythe action of the arms 19 on the wall of the well bore.

The pads 20 are arranged to swing inwardly and outwardly relative to the tool body by means .of individual linkage mechanisms 21 which also serve to maintain the upper and lower portions of each pad substantially paral lel to the longitudinal central axis of the tool bodyr "Although but one such mechanism is to be described, it is to be understood that identical systems are provided for all the pads 20. Linkage mechanism21 includes elongated arms 22, 23 of equal lengthhaving corresponding end portions pivotally connected within housing 17, for example, the end portion of arm .23 is connected at point 23a, The pivotal connections are spaced longitudinally of one another in a longitudinal plane passing through the central axis of the tool and are spaced equal distances outwardly from the central axis. ,Arms 22, 23 extend outwardly of the housingthrough an elongated opening 24Yand their ends are pivotally connected to inner face portions of the pads20 at locationsspaced equal to the longitudinal spacing between the end portions Withinthe housing. Movement of the pads inwardly and outward- 1y from the body is limited by a lower .elongatedarm 25 pivotally connected between aninner face portion of the corresponding pad and movable longitudinally on a lower cylindrical portion,27 of the tool between upper and lower abutment surfaces 28, 29. I

Suitable power means 3!) within the housing 17 istemployed to urge the arms 22, 23 outwardly and, for example, may comprise a compression spring 31 retained between fixed portion 32 of the housingand a driving member 33 movable within thehousing. Cables 34 con. nected'betweenthe driving member 33 and to each arm 23 around eccentric cam surfaces35 thereon to pivot the pads 20 outwardly by the force of the compression spring 31. A hydraulic motor (not shown) may be utilized to retract the arms against the bias of spring 31, if desired. It is to be borne in mind,,however, that the precise details of the linkage arrangement 21 and the power means.

may be left to the discretion of one skilled ,in the :art as other-suitable linkage or power. mechanisms may be employed in harmony withthe instant invention.

The pads 20 may be of any desired type andare illustrated generally asoval-shaped members, each having an.

electrode array 37 '(Fig. 3) embedded within a flexible, electrically-insulating v material.;3 8. such as rubber. A plurality of pivot cars 39 secured, tothe inner surfaceof each pad is used together with appropriate pins to pivotally mount the pads ontheir respective arms 22,23, and 25.- Generally, each pad 20 has an outer wallrengaging surface 40'having a preformed wradius ofrcu'rvature prefa'tubular member 26 slidably erably lying somewherebetween the extremesofcurvature in the range of borehole diameters to beaccommodated'by the apparatus. I In accordance with thepresentinvention', as shown in 1 st'ructed of an; elastic material such .as oil and abrasive- 1 resistant neoprene'rubber having a hardness of approxi- Fig. 4, the supporting armsy19 are elongated f and "have a generally rectangular cross'section. Arms 19 areQconmately -jjdurometers. 'jEacharm has embedded in it, upper and lower supporting members 43, 44 constructed of suitable paramagnetic material such as nonmagnetic stainless steel. The supporting members will be described in detail hereinafter.

Each arm includes a central portion 56 arched outwardly of the housing 16 and which extends longitudinally and generally parallel to the tool body. Central portion 56 has an outer face 56a which is slightly curved in both vertical and horizontal cross section and an inner surface 56b spaced outwardly from housing 16. Spaced outer and inner surfaces 54a,'54b and 55a, 55b, respectively, define integrally connected intermediate portions 54 and 55 which incline inwardly from center portion 56 to adjoining end portions 45, 46. End portions 45, 46 have inner surfaces which are curved to conform to the curvature of the housing and outer surfaces generally of the same'shape. The side surfaces 67, 68 of each arm are generally parallel to one another at the end portions 45, 46; however, in the vicinity of intermediate and central portions 54-56 the .side surfaces are tapered inwardly (Fig. 5). V Each supporting member '43 includes -a .pair of elongated strips or parts 43;: and 43b of rectangular cross section which are pivotally connected together by a hinge and pin connection 47a also embedded within arm 19. The axis of this connection is perpendicular to the longitudinal dimensions of the strips and to a planeintersecting the centralaxis of the tool and the arm, .for' example, the plane defined by lines 44 of Fig. 3. Supporting member 44-likewise comprises .strips 44a and 44b and a hinge and pin connection 47b. Strips 43a and 435 are centrally disposed within the cross section of the arm 19 at its end and intermediate portions 46, 55, while strips 44a,.44b are centrally disposed in the cross section of the end and intermediate portions 45, 54. The hinge connections 47a, 47b are located at the pointsof flexure 61a, 61b for the arm, and housing 16 has an elongated opening 69 positioned opposite .each arm so that when the .central portion 56 is compressed or'fiexed inwardly towards theopening 60, enough of the arm enters the opening so that portions of the arm'at the points of flexure 61a, 61b provide a constant minimum spacing or s'tandoif distance of the tool body from' the well bore when an armis completely collapsed. In the drawings, a distance r measured from the central axis of the body 16 'to the outermost points of fiexure 6111, 611) on an arm less the radius of the body 16 definesthe-rninb mum spacing orstandolf distanceof an arm. To facilitate inward flexure of arm 19, the inner ends of strips 43b, 44b may enterlateral bores-65, 66 inthe central section 56. Each of the end portions 45,46 of the arms is secured to the housing'16by suitablesecuring means such as bolts 50 or thelike extending through bores 51 and threadedly received within the housing'16.

It is, of course, desirable to provide'fiexible arms to facilitate movement through the well bore. However, an elastic material alone is unsuitable since'ithe arms would bend laterally under the mass of the tool thereby failing to space the tool away'from thewalls of the well bore. The supporting members 43, 44 therefore provide the useful function in preventing sidewise distortion or curvature of the arms while simultaneously freely permitting inward and out by. bolts 50 with the arched central portions 56 located .The assembled well bore andat the determined .center of balance 18. tool is then loweredio the bottom of the of' lateral stability forthe arms 19 P the pad contact can 1 r is related to the length subsequently raised to obtain the desired measurements of the well bore or earth formations.

It will be appreciated that the centralizing arms 19 should be slightly larger in diameter than the diameter of the well bore to insure contact with the wall of the borehole thereby permitting centering and balancing of the tool. The force exerted by the arms, of course, varies in relation to the compression of the arms and may, for example, with a tool having arms twenty-eight inches in length, vary from zero compressed diameter of twelve inches to two hundred pounds when the arms are compressed to nine inches in diameter.

It will be appreciated that the arms 19 are flexible yet of sufficient strength to provide a centering action for moderately inclined well bores. For example, in a deviated hole ranging from to 30 degrees of inclination, the arms have a suflicient strength to centrally support the tool (Fig. 1). Within this range of inclination, it will be apparent that the pull of the cable 12 supporting the tool produces a component of force F acting to rotate the upper end of the tool about the fulcrum point or the center of balance 18. Since point of balance for the tool is in a plane through the centers of the arms 19, the force P on the. pads 20 can easily counteract the cable component of force F to maintain the pads 20 in contact with the walls of the well bore. For example, it has been found that for severe conditions of deviation, namely, degrees inclination per one hundred feet of depth or 3 degrees in any 50-foot section, that the component of force F for 1000 pounds of cable pull in a well bore diameter of ten inches is of the order of 27.5 pounds. By providing a force F on the pads greater than the calculated cable component of force be assured under severe conditions of inclination.

Where the deviation exceeds 30 from the vertical, the flexible centralizer arms 19 have been found to collapse inwardly towards the tool (Fig. 2). By providing a controlled dimension r determined by the thickness of the arms and the radius of the tool body at the point of flexure 61a, 61b, the tool body is spaced from the sidewall of the well bore. Of course, the dimension of the tool L between the cable head and the center of balance and the diameter of the well bore so that adequate spacing S of the upper cable head from the wall of the well bore is achieved. The spacing 5 thereby permits balancing of the cable component of force P by the pad force F While the limit of 30 inclination was referred to as the collapsing point of the arms, it will be appreciated that the degree of collapse is dependent upon the amount of force and that a gradual collapsing action can occur.

It will now be apparent from the foregoing that a new and improved arm construction for centralizing means has been provided. Moreover, the centralizing means is flexible and permits centering support of an elongated tool about a center of balance thereby permitting wall-engaging pads to counteract component forces of cable pull in a moderately inclined well bore. 1n highly inclined boreholes, the flexible means provides a minimum spacing of the tool from the sidewalls to permit balancing of the tool which further minimizes frictional forces relative to the pads since the pad force need be only sufficient to counteract the cable component of force. The flexible centralizing means lessens the possibility of the tool becoming stuck in the well bore while pad floating due to contact of the tool body with the walls of the well bore is eliminated by the spacing of the tool body from the sidewalls of the well bore.

Of course, numerous variations can be made in the typical embodiment described above without departing from the scope of the invention. The invention therefore is not to be restricted to the specific form shown by way pounds when the arms have unof illustration, but comprehends all such modifications as come within the scope of the following claims.

What is claimed is:

1. Apparatus adapted for passage through a well bore including an elongated housing, centralizer means positioned about the center of balance of said housing, means to connect said centralizer means to said housing, said centralizer means including a plurality of outwardly bowed, elongated arm members disposed circumferentially about said housing and arranged so as to space the housing from the sidewall of the well bore, said arm members being constructed primarily of elastic material and having end portions and arched central portions, supporting members embedded in said arm members to provide lateral stability for said arm members and to prevent circumferential displacement, said supporting members respectively including first elongated rigid parts in said end portions and second elongated rigid parts in said central portions, and pivotal connections between adjacent ends of each of said first and second rigid parts which lie in a plane parallel to and spaced from the longitudinal axis of said housing, said central portions being pivotal about said pivotal connections whereby the portions of said arm members adjacent said pivotal con-- nections and extending outwardly from vide a minimum spacing of said housing of the borehole.

,2. A centralizing means for apparatus adapted for passage through a well bore including an elongated hous ing, a plurality of elongated arm members spaced circumferentially about said housing and bowed outwardly therefrom so as to space said housing from the sidewall of the well bore, said arm members being constructed primarily of elastic material, said arm members respectively having end portions and an arched central portion, supporting members embedded in said arm members for providing lateral stability and preventing circumferential displacement, each of said supporting members respectively having a first elongated rigid part in one of said end portions and an adjacent, second rigid part in a central portion, said central portion having an opening adjacent to one end of said second rigid part, said sup porting members further including a hinge connection between the adjacent ends of said first and second rigid parts, the axis of said hinge connection being in a plane perpendicular to the longitudinal axis of said housing and spaced from said housing, and means to secure said first rigid parts and the corresponding end portions to said housing whereby said second rigid parts may swing about said hinge connection permitting movement of said central portion towards and away from said housing and whereby the portions of said arms adjacent to said hinge connection which extend outwardly from said housing provide a minimum spacing of said housing from the well bore.

3. Apparatus adapted for passage through a well bore including an elongated housing, centralizer means positioned about the center of balance of said housing, means to connect said centralizer means to said housing, said centralizer means including a plurality of outwardly bowed, elongated arm members disposed circumferentially about said housing and arranged so as to space the housing from the sidewall of the well bore, said arm members being constructed primarily of elastic material and having end portions and an arched central portion, supporting members embedded in said arm members to provide lateral stability for said members and prevent circumferential displacement and respectively including first elongated rigid parts in said end portions and second elongated rigid parts in said central portions, adjacent ends of said second rigid parts in a central portion of each arm member being spaced from one another, and pivotal connections between adjacent ends of each of said first and second rigid parts which lie in planes par allel to and spaced from the longitudinal axis of said said housing profrom the sidewall housing, said central portions being pivotal about said pivotal Connections whereby the portions. of said arm members adjacent said pivotalconn ections and extending outwardly from said housing provide a minimum space ing of said housing from the sidewall of the borehole.

4L A centralizer for apparatus adapted for passage through a well bore including an elongated housing, at least two outwardly bowed elongated arm members spaced circumferentially from one another about said housing, means to connect said arm members to said housing, said arm members arranged on said housing so as to space said housing from the sidewall of the, weil bore, said arm members being constructed primarily of elastic material and having end portions and an arched central portion, each of said arm members having supporting members embedded therein to providelateral stability for said arm members and prevent circumferential displacement, each of said supporting members including a first elongated rigid part in an end portion and part in a central portion of the corresponding arm member, said first and second rigid parts having a pivoted junction with an axis which lies in a plane perpendicular to the longitudinal axis of said housing, whereby said Second rigid part may swing about said pivoted junction and permit movement of said central portion towards and away from said housing and whereby the portion of a second elongated rigid said arm adjacent to said pivoted junction which extends v outwardly from said housing provides a minimum spacing of said housing from the Well bore.

5. Apparatus for logging tool from the sidewall of a well bore including an elongated housing which may be attached to said tool, at least one outwardly bowed elongated arm member constructed primarily of elastic material and disposed onsaid housing so as to space said housing from the sidewall of the Well bore, means to secure said arm member to said housing, said arm member having end portions and an arched central portion, at least one supporting member embedded in said arm member to provide lateral stability for said wall-engaging member 'and prevent circumferential displacement and including a first elongated rigid part, a second elongated rigid part, and a pivotal connection between said first and second rigid parts, said first rigid part being in an end portion and said second rigid part being in a central portion use with and for spacing a well V V 8 whereby the central portion of the pivot relative to the end portion. 7 t

6. A centralizer arm construction comprising: an, elongated arm member constructed primarily of elastic material and having substantially, flat end portions, intermediate inclined portions and an arched central portion, said intermediate portions and central portion having inner and outer surfaces spaced from one another, a supporting member embedded in said arm member to provide lateral stability for said member and prevent cir cumferential displacement and having a first elongated rigid part in one of said end portions and a second elongated rigid part in an adjacent one of said intermediate portions, said first and second rigid parts being connected for pivotal movement relative to one another about an axis disposed transversely to the length of said one end portion and generally perpendicular to a longitudinal plane bisecting said surfaces along substantially the entirety of the length of said arm member.

7. A centralizer arm construction comprising: an elongated arm member constructed primarily of elastic material and having substantially flat end portions, intermediate inclined portions and an arched central portion, said intermediate portions and central portion having inner and outer surfaces spaced substantially parallel to one another; a pair of supporting members embedded in said arm member to provide lateral stability for said member and respectively including a first elongated rigid part in each of'said end portions and a second elongated rigid part in each of said intermediate portions, said central portions having openings adjacent the inner ends of said second n'gid parts, and pivotal junctions between adarm member may and generally perpendicular to a plane bisecting said surfaces along substantially the entirety of the length of said arm member.

References Cited in the file of this patent UNITED STATES PATENTS 2,3 1 1,768 

